Earth Science
PEDOSPHERE LIVING SKIN OF EARTH (SOIL) Soil is made from portions of the geosphere, atmosphere, hydrosphere, and biosphere. It is generally composed of 45% mineral (gravel, sand, silt, and clay), 25% air, 25% water, and 5% organic matter (humus, roots, and dead and decaying organisms). These components reflect the process that formed the soil. § Soil Formation Soil forms when rock weathers. Weathering, or the breakdown of rocks, may result from physical or chemical changes. Soil formation may be slow or a rapid process, depending on the factors at play. Five factors the affect the soil formation: 1. Parent Material - The material or source material is important in soil formation because its chemistry and type will determine the ...